CancerConnect News: The investigative treatment combination including Keytruda® (pembrolizumab) plus Halaven® (eribulin) could provide a potential therapeutic option for patients with advanced triple-negative breast cancer (TNBC) whose disease has advanced following prior therapies. Results of this treatment combination were initially presented at the 2016 annual San Antonio Breast Cancer Symposium (SABCS) and just updated at the SABCS this year.1,2

Approximately 12% of breast cancers are triple-negative breast cancers, meaning that they are estrogen-receptor negative (ER-), progesterone-receptor negative (PR-), and human epidermal growth factor receptor 2-negative (HER2-). This means that TNBC is not stimulated to grow from exposure to the female hormones estrogen or progesterone, nor through an overactive HER2 pathway.

Unfortunately, many available and effective treatment options for the majority of breast cancers block the growth stimulating effects of ER, PR and/or HER2; therefore, TNBC has limited therapeutic options.

In addition, TNBC tends to be an aggressive type of cancer, tends to be diagnosed at a more advanced stage, and proportionately affects younger women more often than other breast cancers. Novel treatment options for TNBC have lagged behind that of other types of breast cancers.

Researchers recently conducted an early-phase clinical trial to evaluate the safety and effectiveness of a treatment combination consisting of Keytruda plus Halaven. Keytruda is referred to as an anti-PD1 agent, and works to stimulate the immune system to identify cancer cells and mount an attack against them. It is currently approved for several different types of cancers; however, it is not approved for the treatment of breast cancer. Halaven is an agent that blocks the formation of certain components in cells that provide structural integrity to a cell, as well as other biologic systems that provide life-sustaining effects to cells. It is approved for the treatment of advanced breast cancer that has progressed following prior therapies.

The data presented at this year’s SABCS included the interim data from 39 patients reported last year and an additional 68 patients. All patients had advanced TNBC that had spread to distant sites in the body, – representing a very difficult stage of disease to treat. All patients received the combination of Keytruda and Halaven.

29% of previously untreated patients achieved an anti-cancer response and 3% had complete disappearance of their cancer.

22% of previously treated patients achieved an anti-cancer response

The median duration of response was 8.3 months, and 14.3% of patients experienced a response for >12 months.

The median overall survival was 17.7 months.

Clinical activity was observed regardless of PD-L1 expression. In those who tested positive for PD-L1 the response rate was 30.6%. In those who tested negative it was 22.4%.

The researchers concluded that it appears that the combination of Keytruda and Halaven provides anti-cancer activity among this difficult-to-treat patient population. The study authors observed that these updated results give us confidence to continue to study Keytruda in the treatment of metastatic breast cancer and we are very encouraged by the activity seen with this combination for patients with metastatic TNBC.”